JPH087860B2 - Magnetic recording media - Google Patents

Description

TECHNICAL FIELD The present invention relates to a magnetic recording medium, and more specifically,
In particular, the present invention relates to a high-quality magnetic recording medium having excellent durability against mechanical damage at the edge portion.

[Conventional technology]

Generally, in magnetic recording media such as magnetic tapes and magnetic disks, magnetic powder is mixed and dispersed with a binder component and an organic solvent to prepare a magnetic coating material, and the magnetic coating material is applied onto a substrate and dried to form a magnetic layer. After forming a magnetic recording medium original material by forming or forming a magnetic layer by depositing a ferromagnetic material such as metal or alloy on the substrate by a method such as vacuum deposition or sputtering, It is made by cutting a raw material of a recording medium into a tape of a predetermined width or a disk of a predetermined diameter by a cutter of a slitter device, a punch and a die or the like.

[Problems to be solved by the invention]

However, in the method of cutting the magnetic recording medium original fabric using the cutter of the slitter device, the magnetic recording medium original fabric is soft even if it is cut into a box shape as shown in FIG. Therefore, as a result of drooping or the like, a part of the cut end face protrudes at an acute angle as shown in (b), (c), and (d) of the same figure, and this acute angle portion strongly hits the train wheel guide or the like and is easily damaged. Further, a large number of cracks are likely to occur in these acute-angled portions, and while traveling in the recording / reproducing apparatus, contact with a guide member or the like may cause the cracks to grow or break, which may adhere to the surface of the magnetic recording medium. It may cause dropout, or may adhere to the head gap and stack to reduce the output.

In particular, in a video tape that requires high density recording, the width of the recording track on the tape becomes as narrow as several tens of μm.
Trace accuracy with the head for signal recording / reproduction is required, and for this reason, a large number of guide guides for forcibly running along the tape edge are provided for positioning during tape running. For example, FIG. The tape guide band 14 of the lower cylinder 13 forming the VTR rotary head system as shown in Fig. 4 is provided. When the video tape 1 passes through such a regulation guide, the sharp edge portion of the tape edge portion strongly hits. As a result, the relative position between the head and the tape changes due to the wear of the tape edge and the buckling damage of the protruding acute angle part, the trace accuracy of the recording track deteriorates, and the head reproduction output fluctuates. In addition, the sharp edge of the tape edge may be broken or peeled off to adhere to the surface of the magnetic recording medium or the head gap, causing dropout or lowering the output. To do.

[Means for solving problems]

The present invention has been made as a result of various studies in order to solve the above drawbacks.
Prevents mechanical damage to the edge of the magnetic recording medium by creating a gentle convex curved surface that fits within a range surrounded by two concentric circles, a circle with a diameter of 1.2 times and a circle with a diameter of 0.8 times. Suppress the occurrence of cracks at the edge,
It is intended to prevent a dropout and a decrease in output due to these, and to obtain a high-quality magnetic recording medium excellent in durability against mechanical damage.

In the present invention, the cross section of the edge portion of the magnetic recording medium is, as shown in FIG.
The cross-section 21 in the thickness direction of the magnetic recording medium 1 is within a range surrounded by two concentric circles, a circle A having a diameter 1.2 times the thickness t of the magnetic recording medium 1 and a circle B having a diameter 0.8 times the thickness t. A convex curved surface is preferable, and an arc-shaped convex curved surface having a diameter 1 times the thickness t of the magnetic recording medium 1 is most preferable.

A cross section 21 in the thickness direction of the edge portion 2 of the magnetic recording medium 1 is
Such a gentle convex surface causes buckling damage due to stress concentration by coming into contact with the regulation guide of the magnetic recording / reproducing apparatus like an acute angle portion of the edge of the magnetic recording medium cut by a conventional cutter. In addition, the gentle convex curved surface of the cross section 21 of the edge part reduces the contact force with the regulation member, which can keep the track tracing accuracy high and improve the durability against mechanical damage of the edge part. A high-quality and highly reliable magnetic recording medium can be obtained.

On the other hand, the tip of the convex curved surface of the cross section 21 of the edge portion is the second
As shown in Figure (a), when the circumference circle A is exceeded, the tip of the convex curved surface projects and stress concentrates easily, causing damage.
As shown in the above, when the outer peripheral circle A is entirely crossed, the thickness of the edge portion increases in spite of no concentration of stress, and for example, in the case of a magnetic tape, the winding diameter on the reel becomes large, which makes it impossible to fit in the cassette case. is there. Further, as shown in FIG. 3C, when the tip of the convex curved surface enters the inner diameter of the inner circumference circle B, the convex curved surface does not become gentle and the upper and lower points are sharpened, stress concentrates and is easily damaged.

For each such thickness of the magnetic recording medium, 1.
An edge portion of a magnetic recording medium having a gently convex curved surface that is contained within a range surrounded by two concentric circles, a circle having a diameter of 2 times and a circle having a diameter of 0.8 times, is, for example, the magnetic recording medium original shown in FIG. It is formed by a method of irradiating a raw material of the magnetic recording medium with a laser beam to cut the raw material, using an anti-cutting device.

Hereinafter, description will be given with reference to FIG. 3 showing an embodiment of the magnetic recording medium original fabric cutting device.

In FIG. 3, 3 is a laser oscillator, and a laser beam 4 emitted from this laser oscillator 3 is reflected by a mirror 5, passes through an optical system 6, and is converged by a condenser lens 7,
It passes through the inside of the gas nozzle-shaped processing head 9 provided coaxially with the optical axis of the converged light 8 and below the processing head 9.
The magnetic tape stock 10 traveling at a considerable speed in the direction of arrow C is irradiated.

By the irradiation of the convergent light 8 of the laser beam, the laser beam irradiation spot 11 of the magnetic tape raw material 10 running below the processing head 9 is heated and locally becomes a high temperature of several hundred to several thousand degrees, and the magnetic tape The raw material 10 is instantly liquefied, vaporized or plasmaized to be removed and cut.

Here, the laser beam to irradiate the magnetic tape original fabric 10 is
It is preferable that the output per cutting portion is within the range of 20 to 800 W, and the diameter of the laser beam irradiation spot 11 is as small as possible within 6 times the total thickness of the magnetic tape original fabric 10. When the laser beam irradiation spot 11 irradiates the convergent light 8 of the laser beam, the cross section 21 in the thickness direction of the edge portion 2 of the magnetic tape 1 as shown in FIG. It is possible to make a gentle convex curved surface within a range surrounded by two concentric circles, a circle having a double diameter and a circle having a diameter of 0.8 times. On the other hand, if the output of the laser beam per cutting unit is less than 20 W, the cutting efficiency will be reduced or defective cutting will occur, and if it is more than 800 W, the laser oscillation modes will be multiple and the laser beam will have good focusing properties. Since no light is obtained, inconvenience occurs such that heat is applied to the cut portion. Further, if the diameter of the laser beam irradiation spot 11 is larger than 6 times the total thickness of the magnetic tape original sheet 10, the utilization efficiency of the laser energy for cutting is reduced, and the edge section cross section is damaged due to heat damage around the cutting section. There is a problem that a good convex curved surface cannot be obtained and a tape winding diameter increases, which causes a problem in assembling in a cassette. Therefore, it is preferable to bring the spot as close as possible to the minimum spot limited by the laser light wavelength.

Reference numeral 12 denotes a gas introduction pipe attached to the peripheral wall of the processing head 9 in the shape of a gas nozzle. During cutting of the magnetic tape raw material 10, an assist gas such as nitrogen gas is introduced from the gas introduction pipe 12 into the processing head 11. A gas flow is ejected in the direction of the laser beam to efficiently remove the liquefied, vaporized or plasmated end of the magnetic tape stock, controlling the thermochemical reaction and preventing the oxidation reaction.

As the laser oscillator 1 used in such a cutting device for the magnetic tape material 8, a CO ₂ laser, a YAG (yttrium-aluminum-garnet) laser, an argon laser, or the like, which is usually used as a laser oscillator, is used. However, any of them is preferably used without any particular limitation.

In addition, when the edge section cross section 21 is formed into a gentle convex curved surface as described above, it is not always necessary to perform irradiation with a laser beam, and after cutting the magnetic tape original fabric with a cutter or the like, laser light is first applied. Irradiation may be performed to make the cross section of the edge portion a gentle convex curved surface as described above.

Further, although the magnetic tape has been described above, the same effect can be obtained not only in the case of the magnetic tape but also in the case of a magnetic disk, in which the section of the edge portion can be the gentle convex curved surface as described above.

The formation of the magnetic layer on the substrate in the original magnetic recording medium is
γ-Fe ₂ O ₃ powder, Fe ₃ O ₄ powder, Co-containing γ-Fe ₂ O ₃ powder, Co
Containing Fe ₃ O ₄ powder, CrO ₂ powder, Fe powder, Co powder, Co-Ni
Alloy powder, Fe-Ni alloy powder, Co-Ni-P alloy powder, Co-
Various conventionally known magnetic powders such as Ni-Fe alloy powder and barium ferrite powder are coated on a substrate together with a binder resin and an organic solvent and dried, or Co, Ni, F
A method in which a ferromagnetic material such as e, Co-Ni, Co-Cr, Co-P, or Co-Ni-P is deposited on the substrate by means such as vacuum deposition, ion plating, sputtering, and plating. Is formed by. Then, if necessary, a backcoat layer coating material prepared by mixing and dispersing a filler, a binder resin and the like with an organic solvent is applied to the back surface of the substrate having a magnetic layer formed on the surface and dried to form a backcoat layer. It is formed.

Here, as the binder resin used for forming the magnetic layer, for example, vinyl chloride-vinyl acetate copolymer, polyvinyl butyral resin, fibrin resin, polyurethane resin, polyester resin, etc. Those used for recording media are widely used, and as the organic solvent, conventionally used organic solvents such as methyl isobutyl ketone, methyl ethyl ketone, cyclohexanone, ethyl acetate, dioxane, benzene, toluene, and xylene are used alone or. Used as a mixture of two or more kinds.

As the substrate, any of those generally used as a substrate, such as a polyester film, a polyamide film, a polyimide film, is preferably used.

〔Example〕

 Next, an embodiment of the present invention will be described.

Example 1 Co Coated γ-Fe ₂ O ₃ powder 100 parts by weight Nitrocellulose HIG1 (Asahi Kasei Corp., nitrocellulose) 10 parts by weight Estane 5702 (Goodrich Chemical Co., urethane elastomer) 9 parts by weight Coronate L (Japan Polyurethane) Kogyo Co., Ltd., trifunctional low molecular weight isocyanate compound) 1 part by weight granular α-Fe ₂ O ₃ powder 5 parts by weight carbon black 5 parts by weight zinc stearate 0.5 parts by weight-n-butyl stearate 0.5 parts by weight toluene 80 parts by weight Methyl ethyl ketone 80 parts by weight Cyclohexanone 80 parts by weight This composition is mixed and dispersed in a ball mill for 72 hours to prepare a magnetic paint, and the magnetic paint is applied on a polyethylene terephthalate film having a thickness of 9 μm so that the dry thickness is 3 μm, and dried. Then, a magnetic layer was formed and a videotape original fabric was made.

Then, the obtained video tape original is run under the processing head 9 of the magnetic recording medium original cutting device shown in FIG. 3, a CO ₂ laser with an output of 400 W is used as the laser oscillator 3, and the converged light 8 is emitted. The diameter of the laser beam irradiation spot 11 of 50
After irradiating to a size of μm, it was cut into a predetermined width to make a video tape.

Comparative Example 1 In the cutting process by the laser beam in Example 1, the original tape of the video tape was cut in the same manner as in Example 1 except that the diameter of the laser irradiation spot 11 of the convergent light 8 was changed from 50 μm to 200 μm. I made a tape.

Comparative Example 2 In Example 1, instead of cutting with a laser beam,
A video tape was produced by cutting the raw material of the video tape in the same manner as in Example 1 except that the width was cut by a normal cutter to a predetermined width.

The shapes of the cross sections of the edges of the video tapes obtained in the respective examples and comparative examples were observed using a scanning electron microscope. The video tape obtained in Example 1 is shown in FIG. As described above, a gentle convex curved surface 21 is formed within a range surrounded by two concentric circles, a circle A having a diameter 1.2 times the thickness t of the video tape 1 and a circle B having a diameter 0.8 times the thickness t. It was Further, in the video tape obtained in Comparative Example 1, the lower end portion of the convex curved surface 21 greatly protruded below the outer circumference circle A as shown in FIG. As shown in (c) of the figure, the tip of the convex curved surface 21 blurs the inner diameter of the inner circumferential circle B, does not form a gentle convex curved surface, but the top and bottom are sharp, and the lower end portion protrudes forward from the outer circumferential circle A. It was

Moreover, the video tapes obtained in the respective examples and comparative examples were manufactured by using a VTR and VT-7 manufactured by Hitachi Ltd.
The output fluctuation was investigated after repeatedly running 200 times at ℃ and 80% RH.

 The results are shown in Table 1 below.

The video tape obtained in Comparative Example 1 could not be wound up for 2 hours on a 2-hour type (T-120) reel.

〔The invention's effect〕

As is clear from Table 1, the video tape obtained in Example 1 has less output fluctuation than the video tape obtained in Comparative Example 2, and the video tape obtained in Comparative Example 1 has an edge. Although the lower end of the partial cross section is excessively raised, the winding diameter of the tape is increased to cause a problem in assembling the cassette, but the video tape obtained in Example 1 does not cause such a problem.

From these facts, the magnetic recording medium obtained by the present invention has excellent durability against mechanical damage to the edge,
It can be seen that this is a high-quality magnetic recording medium in which there is little fluctuation in output due to mechanical damage to the edge and there is no problem in assembling the cassette.

[Brief description of drawings]

FIG. 1 is an enlarged cross-sectional view of the cut portion of the magnetic recording medium obtained by the present invention, and FIGS. 2 (a), (b) and (c) show the cut portion of the magnetic recording medium obtained by the conventional method. FIG. 3 is an enlarged cross-sectional view, FIG. 3 is a schematic perspective view showing an example of a magnetic recording medium original cutting device used in the present invention, and FIG. 4 is an enlarged cross-sectional view of a cutting portion of the magnetic recording medium obtained in Examples and Comparative Examples. FIGS. 5 (a), 5 (b), 5 (c) and 5 (d) are schematic cross-sectional views of a cutting portion of a magnetic recording medium obtained by cutting with a conventional cutter, FIG.
The figure is a perspective view of the lower cylinder of the VTR rotary head system. 1 ... Magnetic recording medium, 2 ... Edge portion, 21 ... Cross section, t
...... Thickness of magnetic recording media, A, B …… Yen

Claims (1)

[Claims] 1. A range surrounded by two concentric circles, a circle having a diameter 1.2 times and a circle having a diameter 0.8 times the thickness of the magnetic recording medium. A magnetic recording medium having a gently curved convex surface that fits inside.